[time-nuts] Re: HP Z3801A info needed - 1PPS interface

[paul swed]

Ed I seem to be a bit slow. Had not heard of your project.
On the real 3801 the 25 pin connector is actually RS 422.
Regards
Paul
WB8TSL


On Tue, Oct 5, 2021 at 3:11 PM ed breya <eb at telight.com> wrote:

> I've been doing a bit more work on the far from finished Z3801A project,
> trying to button things up. It has been sitting for years all opened up
> (but running), with temporary pieces and cables and wiring hanging out
> every which way. The next piece I want to get going is the 1 PPS
> interface, to provide the signal out, and to run the clock. In the
> manual it says the 1PPS signals are on the DB-25 connector, in
> differential "pseudo-ECL" form, but that's all - no level or common-mode
> info is provided. Online searching the term seems to indicate it's just
> PECL - Positive ECL running from +5 V, with everything shifted up
> accordingly. That's just fine (and easy to implement), as long as I know
> what to expect. I figured I'd check here to see if that's correct, or if
> it means something else in the Z3801A context. I'll find out eventually
> when I start fooling with it, but right now it's buried deep in the guts
> of the box, so not easy to scope out yet until I start hooking it up and
> designing the interface.
>
> A related question is, is there any particular generally accepted or
> favorite spec or description of the 1PPS signal output from the BNC?
> I'll probably make it 0/+5 V out, fairly strong, with the leading
> positive edge being the official tick mark. The clock will use a
> softened up version. The DF will be whatever the Z3801A puts out.
>
> Ed
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